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Zero Flight Experience to Light Jet Type Rating - Requirements, Feasibility, and Timeline?
Hi everyone I have read this form for a couple months I am someone who is extremely interested in getting my private pilots license. But I am curious about something if I was to at some point secure a very high paying job or come across a boat load of cash and I wanted to invest in a light jet like a Phenom 300 or a CJ3+ would it be possible, in a reasonable amount of time, to go from being a VFR pilot to a type rating for single pilot flight in one of these jets? What would the timeline look like? what are the requirements are there? My understanding is the biggest hurdle is insurance. I'm really just curious so sorry to bother everyone. I have no idea what the future holds but being able to fly one of these incredible machines would be a dream come true.

Aside from the costs, not to mention an insurance company willing to provide you hull insurance on an airplane like that, your chief difficulty is going to be building the experience and seasoning to move into high-performance jet aircraft.
I would argue for a minimum of 300 hours of total flight time before advancing onto a jet like that, with at least 50 hours of instrument and multi engine time and solid cross country experience simply to give yourself enough seasoning to be ready to move into a high-speed environment like that.
Legally to serve as Pilot In Command (PIC) on an airplane such as a CJ3, under Part 91 recreational flight operations, you are going to have to hold the following:

At least a Private Pilot’s Certificate, with an Airplane, Multi Engine Land rating.
An Instrument-Airplane Rating.
An High Altitude Airplane endorsement.
A current unrestricted type rating on the CitationJet.
A current FAA Medical Certificate, Third Class or better.

The first place to start would be obtaining a private pilot certificate with an airplane, single engine land rating.  One could attempt to obtain a PPL with an airplane multi engine land rating right off the bat, but this is inevitably more expensive and time-consuming, and, unless you own the airplane, it will be very difficult to talk a flight school into letting you solo in such an aircraft, not to mention insurance companies, so we will stick with the ASEL rating on your PPL for now. If you have the time and commitment for hard-core study, you could probably knock this out in about three months and meet all the requirements listed in part 91 to obtain a PPL.  Once that is done, you  will obtain your instrument rating.  Expect that this will consume at least another three months or so worth of serious study and at least a couple of flights a week.  When this is complete, you will be ready to obtain a multi-engine, land add-on.  This will typically require a complex and high performance airplane endorsements as well. Once that is all finished and assuming to you can keep up with the workload, your next challenge is going to be to start logging a lot of instrument flying as well as VFR flying To a variety of different airports and locations, and varying weather and night conditions.  We’re gonna have to start building experience and getting used to flying in high-speed, high density traffic environments as a preparation for moving into jet airplanes. I would say expect to spend 200 to 300 hours of time building at this point to get such experience.  Once that is complete, and you acquire a CJ3, you will begin your type rating training as well as acquire your high altitude, endorsement needed to fly those.  Once you have a CJ3 type rating, you will still need to log 25 additional hours with an authorized instructor and undergo a final practical test to have the SIC required limitation removed and be issued an unrestricted type rating in the CJ.
As of this point, you’re legally authorized to fly a CJ3 single pilot.
Your currency on the CJ3 type is only good for 12 calendar months and must be renewed with recurrent type rating training followed by another practical exam in order to maintain currency.
Bear in mind the following: Flying airplanes is an art and one that can become very dangerous to you and others if carelessness, incapacity, or neglect is demonstrated by the pilot.  You’ve reached the point that you can be a journeyman in your CJ3 flying, but you’ve got approach that with a dose of humility and realize that you’re very, very green at this stage of your flying career.  At a bare minimum, you’re going to have several hundred hours worth of additional flying on your own, setting very conservative personal minimums in regards to locations you fly the aircraft in and out of, weather minimums, crosswind, minimums, runway length minimums, etc.  As with any other hobby, start simple and work complex. You may not be ready to casually fly off to KJFK or KATL at this point but with time and practice it can happen.

Thank you so much! This is just a pipe dream of mine. I’d love to be able to go cool places with family and friends. You make fantastic points about safety and experience, it would be quite a journey to do this and do it right. While I am almost certain this dream will never come true it’s awesome to think about. Hopefully one day I can learn to fly even if I just get a basic PPL. Thank you for your time!

@FootballFan1846 to further drive home the point of cost and safety: to remain current and thus safe you would have to fly a lot more than 100 hours a year. Even with that you are most likely not as safe pilot as a professional one. For information regarding cost, safety and all that jazz, AOPA is a tremendous resource

@Jpe61 not correct

@Cloud so a private pilot flying a small jet less than 100h/year is as safe as a professional pilot?

You didn't state professional. The minimums for maintaining a PPL are well below 100 hours a year. Actually they're well under 50 hours per year!

@Cloud ... in a SEP! For a jet like the Citation I'd want to be doing at very least a hundred or so hours. What is strictly legal, and what is sensibly safe, are very very separate.


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Designing an attitude indicator - Having issues with inclinometer
This is my first post.
I am currently building a project for a fixed wing microlight aircraft (UK). The project is a flight computer based around an Arduino and a 4D Systems touch screen. The primary screen is a digital attitude indicator with various EFIS functions. I'm using this sensor currently for pitch and roll:
https://witmotion-sensor.com/products/military-grade-accelerometer-inclinometer-hwt901b-mpu9250-9-axis-gyroscope-anglexy-0-05-accuracy-digital-compass-air-pressure-altitude-rm3100-magnetometer-compensation-and-kalman-filtering
All is good on the ground and I am using the angle output over TTL to determine relative angle. Works perfectly and pitch and roll all display exactly as expected. In the air the pitch works well but roll does not. It's like the sensor is detecting angular acceleration and not absolute angle. As you start to roll the attitude indicator shows the deflection but once stable in the turn it returns to level even though the plane is still banking. As you roll back to level it swings the other way and then settles again.
I am assuming that this is due to the way forces are acting during a turn i.e. the 'downwards' force is perpendicular to the direction of flight and the sensor is getting confused. The sensor has 6-axis and 9-axis modes and both show the same result.
I wondered if anyone else had attempted such a project and what sensor they had used? It's obviously possible to do this using digital sensors as there are plenty of digital AI on the market. I'm happy to try a different sensor but don't want to buy another one until I am fairly sure it's going to work in the air.
Thanks for any assistance! Tim

See my comment here https://aviation.stackexchange.com/questions/106008/designing-an-attitude-indicator-having-issues-with-inclinometer#comment295422_106009  -- the title of the question perhaps could be improved, unless you really are relying only on the linear acceleration (inclinometer) functions of the sensor.

You say "In the air the pitch works well but roll does not."  -- have you tested the pitch function while looping?  I suspect you would find that would not work well either.  I.e. I suspect you have a problem with pitch indication that is symmetrical with the problem you are having with roll indication, but you haven't maneuvered the aircraft radically enough to see it.

Probably poor use of the work inclinometer - The device is a 9-axis gyro, accelerometer, inclinometer that uses a fusion algorithm to output an absolute angle value in X,Y and Z axis. On the ground that works perfectly - the odd behavior is only in flight where the forces of gravity are obviously acting very differently.
Sadly, I am not rated for aerobatics so no looping for me :D

The fusion algorithm is black-box - i.e. I don't know exactly how it's doing it's magic. There are options for 6-axis and 9-axis algorithms and both do the same thing.

An inclinometer is fundamentally the wrong tool to measure bank angle. In a coordinated turn, the local acceleration is along the aircraft's vertical axis. An inclinometer does the same thing as the ball in a traditional six pack, not the attitude indicator.
You need some sort of gyroscope to measure roll rate. This roll rate can be integrated to get bank angle. You also need to implement some system to correct for integration errors in the bank angle- essentially what the pendulous vanes do in a tradition vacuum-powered AI.
It looks like the instruments you need are available in the module you've linked and you're just reading the output of the wrong one.

If you follow the link to the sensor included in the original post, you'll see that it includes gyroscopic sensors.  The unit is described as "9 axis", which appears to refer to linear acceleration, rotational acceleration, and magnetic field sensing, each in all three axes.  I suspect the title of the question is misleading.  The body of the question does not suggest that the asker is relying on only the linear acceleration sensors (which is what "inclinometer" would suggest.

@quietflyer "using the angle output over TTL" and the described way it is working (works on the ground, shows indication when rolling into a turn but then levels immediately) both sound like they are using the inclinometer to me. At the very least that is consistent.

Apologies - I probably used the wrong term as the module is described as a "Accelerometer+Inclinometer" - The module itself is a 9-axis device using a fusion algorithm to output a number of data-feeds. The data feed I am using is the "Angle" feed which is an X,Y,Z absolute position angle driven by the 9 axis algorithm.
On the ground this works perfect as described but does not work until the forces of flight.

@TimG What other data feeds are available? Does the pitch output work properly under more aggressive maneuvers like a pushover?

Outputs are: Acceleration XYZ|A|, Angular Velocity XYZ|W|, Angle XYZ, Magnetic Field XYZ|H| and Quaternion Q0-3.

Not sure on really aggressive maneuvers - I'd say it may be a bit off based on take-off angles.

This sounds to me like the item Chris mentioned is necessary is present but just turned up way too high.

You also need to implement some system to correct for integration errors in the bank angle- essentially what the pendulous vanes do in a tradition vacuum-powered AI.

The materials for this module suggest that it does this sort of correction.
The question is what sort of timescale it does that correction.   The roll and pitch rate have errors, but over a long time scale, you assume your plane is flying level and you have your sensor zero them out.
Could be the algorithm is just too aggressive and is zeroing it out over seconds instead of many minutes.   I would look at the datasheet and see if you have any control over the integration time for the corrections.

That's what occurred to me reading the question as well. In a traditional gyro-powered artificial horizon, the instrument corrects for precession errors by leveling the wings (i.e. zeroing the indicated roll angle) when showing a very small bank angle. If you hold a 30-degree banked turn, the instrument shows that bank angle as long as you maintain it; if you maintain a turn with a 5-10 degree bank, the gyro will "correct" its precession, and return to wings level. Sounds like the logic in OP's instrument is doing this, but not only at small bank angles.

I am using the angle data feed which is an absolute X,Y,Z position measurement - supposedly drawn from a fusion algorithm. On the ground this works perfectly for small and high angles over both short and long term measurements. So it works well for 5-10 degrees and 30 degrees over 1 second or 10 minutes. It's only in the air that the measurements seem to be incorrect.

Interestingly I just found this which is the exact issue I am seeing
“Sustained dynamic accelerations can cause a problem in the estimation of the pitch and roll angles as the assumption that the accelerometer is measuring gravity alone is constantly being violated. The most common case where this becomes a significant problem for an AHRS is when an aircraft is operating in a banked turn. When this occurs, the accelerometer measures gravity plus a long-term acceleration due to the centripetal force created by traveling along a curved path. This results in a measurement vector that acts perpendicular to the wings of the aircraft and cause the AHRS to estimate a roll angle of zero while the aircraft is in fact in a banked turn and thus has significant roll relative to the horizon”
https://www.vectornav.com/resources/inertial-navigation-primer/theory-of-operation/theory-ahrs
Looks like there is a workaround using velocity measurements. I’ll need to do some reading and see why I can do.

The key question would be, can the system stop "correcting" the roll angle based on sensed gravity? Or at least, only do it under certain conditions (such as, small roll angle & no heading change being observed). The vanes in @Chris' answer do that - only zero out the roll toward the sensed gravity vector when the roll angle is small. No idea if such settings inside your AHRS are accessible to the user, or not.

PS as an aside I am a guy who used a home-made solid state piezoelectric single-axis turn rate indicator (actually closer to "turn coordinator" because gyro sensing axis was tilted) created by a friend to maneuver a hang glider in clouds. Output was very primitive, just 3 LEDs that blinked at varying rates depending on turn rate and direction.  It worked fine, at least the few times that I tried it.  Gained about 2K thermalling in a cloud once, then icing. Always intended to upgrade to some sort of AHRS-based 3-axis system and actually ordered the sensor unit, but never got around to using it-

That’s super cool. I started flying hang gliders 15 years ago and moved over to flexwing Microlights (and also now three-axis). Flying in cloud is not something I would ever have desired to do in a hang glider - respect to you.

I think the answer is not to use the fusion angle output. Rely on the gyro outputs to determine roll and then use the accelerometer to zero the gyro when in level flight. 95% of the flight is going to be level so it should not be too much of an issue to zero out the drift. I’ll have a think about it.

@TimG -- not saying it was very smart... !!

@quietflyer - if nothing else. I’m sure it makes for an amazing anecdote over a few beers!

I’ve been doing some research on various projects that share similarities. Mainly ArduPilot. Looks like it requires an extended Kalman filter and not just the standard KF that my sensor comes with. I can access the raw data from the gyro etc so I guess I’ll need to see if I pull that into a better algorithm to work out real roll and pitch in flight.
Feels like it’s possible but not insignificant from a computational perspective. I have my work cut out but at least I roughly know where to go with it.

Have you advanced with this?
This is a basic problem with accelerometers/gyros due to centripetal force in coordinated turns.
It can be solved using an extended kalman filter that takes a GPS reference.
Take a look at https://github.com/FlyTheThings/uNavINS for an implementation that works with a UBlox NEO-9 GPS module.
I have built an AHRS system using an ESP32 and this code and it works perfectly (many hours of flight time tests).

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What happens to aircraft wreckage?
A small private plane (Piper) crashed near where I live a few years ago. Both occupants were killed. The crash site is on the top of a ridge in dense forest. Reaching the site would require a hike of about a mile from the nearest road. The terrain is steep, heavily wooded, and crossing several creeks would be required. No vehicle can reach the site, not even ATVs.
I spent a number of years as an EMT with the fire department, so I know how the initial rescue goes and what happens to the human remains, but what happens to the wreckage and who takes care of it? The fire department certainly isn't going to invest the time and manpower it would require to haul that plane out of there.
In this example, you would have to use a helicopter to remove the wreckage. Even if you disassembled it on site, carrying it out would still be impractical (there's that engine to deal with, for one).
So for the investigators on a crash like this, do they travel to the site to inspect the plane, do they retrieve only key pieces, or do they just do without?
And to what extent does that depend on the size of the plane and number of victims? For example, do they leave the single-engine Piper where it is but haul out pieces of the 747 by helicopter?
Any info you'd like to add on salvage would be appreciated too. Crashed or not, a plane is likely to contain some valuable and undamaged electronics, engine parts, etc. Surely that stuff isn't just left for whoever wants it to salvage.

@ZachLipton Knowing what VHF radios, instruments, GPS units, etc. can be sold for on eBay, I expect plenty of people would be willing to salvage stuff like that. If the plane didn't burn (this one didn't) and the cockpit isn't totally destroyed, I would expect there's a good chance some or even most of that stuff will be perfectly functional.

Somewhat related: How is an airplane towed/recovered after an emergency off-field landing?

I'd take a radio if it had a yellow tag.

Depending on the size of aircraft, it's quite practical for helicopters to sling completely assembled yet, wrecked aircraft back to a road system.

Most planes are insured for hull value also. So the insurance company owns the aircraft after the claims are paid.

It depends on a lot of things like the kind of accident, the wreckage state, accessibility etc.
First thing to consider is that in most cases, the wreckage is evidence- so the investigating authority will take control of it and release it only when the investigations are complete or has reached a stage where the wreckage is not needed anymore.
As far as air investigations are concerned, the first thing to do usually is to dispatch a team to the site. For example, NTSB has a 'go' team which is dispatched as soon as possible to the accident site. From NTSB site:

At the core of NTSB investigations is the "Go Team." The purpose of the Safety Board Go Team is simple and effective: Begin the investigation of a major accident at the accident scene, as quickly as possible, ...
During their time on the "duty" rotation, members must be reachable 24 hours a day by telephone at the office or at home, or by pager.

After a preliminary investigation, the team decides what to do with the wreckage- either these are returned to the owner or retained for further investigation, partially or in full. From NTSB Major Investigations Manual:

When the IIC and the group chairmen have determined that parts or all of the wreckage is no longer needed for investigative purposes, the IIC ..., in consultation with the OAS Director, will be responsible for preparing and signing Part I of the wreckage release form (NTSB form 6120.15). The form shall be executed by the NTSB representative and signed by someone acknowledging his/her receipt of the wreckage This is done in almost ll cases, except those where there is no accessibility to the wreckage, like he ocean floor.
Part II of the wreckage release form will include a detailed list of any parts or components of the wreckage that will be retained by the NTSB for further examination.

Note that the release of wreckage is decided by the investigating authority and it may be kept in storage, if necessary.

There should be no pressure to release all of the on-scene wreckage. Often it is better to arrange for wreckage removal and storage and to retain control of the wreckage in case there is a need to examine it later.

In some cases, the investigating authority will go to great lengths to transfer the wreckage to their place, so as to carry out full investigation. This happened in the case of TWA 800 investigation, where the wreckage was picked up from seafloor and reconstructed to investigate criminal activity.

Image from the NTSB aircraft accident report (NTSB/AAR-00/03) fig. 29, page 102, via Wikimedia Commons.
Another thing is that the disposal of wreckage is a costly business when its done. This is where the size and location of the wreckage comes in. Most of aircraft wreckage would be aluminum scrap, usually too expensive to move and too uneconomical to use elsewhere. Obviously there's a difference between a 747 wreckage downtown and a R-22 wreckage in a remote hill (I'm taking about wreckage disposal, not investigation here). The disposal is done either by the owner/insurer or the investigating authority, with the owner/insurer coughing up. From Singapore Investigation of Accidents Statute:

If  a  person  to  whom  custody  of  the  aircraft, parts,  wreckage  or  contents  is  to  be released refuses to take custody thereof or fails to take custody within a reasonable period, the  aircraft,  parts,  wreckage or  contents  may  be  disposed  of  in  such  manner  as  the  Chief Inspector considers fit.
The  expenses incurred  by  the  Chief  Inspector  in  disposing  of  the  aircraft,  parts, wreckage  or  contents  shall  be  borne  by  the  owner  or  operator  of  the  aircraft  and  be recoverable from either or both of hem.

Most other countries have similar rules. As for reusing the contents in the wrecked aircraft, this is usually not permitted (though it depends on the operator/regulator rules). In case it is permitted, the LRU logbook should contain details about it being in an accident and in general, they are sent to OEMs for tests and recertificaiton. Some companies do trade in salvaged aircraft.
And finally the 'stuff' is sometimes left to salvage for whoever wants it- it may be the most economical thing to do, after all.

And sometimes parts remain on site for decades.  I've stumbled across two sites in the hills hereabouts where there are some parts, identifiable as such by anyone familiar with small planes.

In many areas of the Rockies there are many aircraft wrecks littering the mountains.  Often the investigators will remove just the minimum necessary to get their job done.  If the pilot survived and could clearly explain that he got caught in a downdraft (a very common occurrence) that pushed him into the mountainside there's no reason to waste time and money trying to retrieve the wreck.  In these cases, the wreck gets painted with a big orange X so the next time there's a search and rescue operation they can identify it as an old wreck.

@Gerry What could I search to see some pictures of those big X marked plane crash sites?

It's the same in Greenland. Often various plane wrecks are all that's visible on a whit background for miles around, particularly on the ice-cap around Kangerlussuaq.

Depending on severity, damaged planes can also return to service after being repaired. The Gimli Glider is an example.

There are a few questions here so I'll address them individually (this also varies by jurisdiction).
For similar reference you should read up on Lauda Air Flight 004 which lead to a similar situation.
First off an aircraft accident (at the moment it happens) becomes an open investigation. It is a crime to tamper with aircraft wreckage (this includes simply moving it (which you can do if you feel there is danger as a result of it)). If you come across a wreck you should leave it as is. But none the less, generally speaking the FAA/NTSB will be called to the site to begin the investigation post crash. Its important to find out what happened and why it happened in case there is a defect to the aircraft that needs to be dealt with. In many cases the investigators will remove the wreck and reassemble it elsewhere to carry out most of their investigation. The site is often photographed and documented before this happens but investigations can take a long time and the process can be tedious. This is the general case and of course the outcomes vary case by case.

So for the investigators on a crash like this, do they travel to the
  site to inspect the plane, do they retrieve only key pieces, or do
  they just do without?

There is generally travel to the sight to at least photograph and investigate in more severe accidents, in some cases the NTSB relies on your report alone (if there are survivors or witnesses). In some regards it's up to them in terms of removal. With GA incidents the planes are far simpler and the accident causes in some cases are straight forward. If they need to retrieve the whole plane for the investigation and the believe it's possible, they will. For example the wreckage of JFK Jr's Piper Saratoga was retrieved from the ocean floor to complete the investigation.

And to what extent does that depend on the size of the plane and
  number of victims? For example, do they leave the single-engine Piper
  where it is but haul out pieces of the 747 by helicopter?

Generally none, it's important for the NTSB to complete all investigations and they take them all seriously.

Any info you'd like to add on salvage would be appreciated too.
  Crashed or not, a plane is likely to contain some valuable and
  undamaged electronics, engine parts, etc. Surely that stuff isn't just
  left for whoever wants it to salvage.

Generally speaking you can't do this legally. First off most of the parts on the airplane are no longer airworthy (there may be a law about parts that have been in a hull loss accident) but on any note you most likely can't get the logs for the plane and thus can't objectively prove the hours on the airframe (thus the parts are not airworthy).

Do items like radios require a history and get certified as airworthy the same way airframe parts do?

Ron, Good point ill update to reflect.

most of the parts on the airplane are no longer airworthy There are companies like Dodson Int'I that resell parts and a large part of their stock comes from crashed aircraft. They have a large field covered with wrecked airplanes and helicopters.

Very true there are companies that do it but they have the means/ability/knowledge to obtain the logs and deal with the paperwork. One can not simply pull a part off a wreck in the woods and sell it per say.

It's important for the NTSB to complete all investigations and they take them all seriously. In principle true, but the NTSB takes major accidents (airliners) much more seriously.  Partly this is because small aircraft have accidents much more often, but also because crashers of airliners have much more public attention.  As for getting the aircraft logs... the logbooks are often not kept in the plane and therefore would usually survive a crash, even if the pilot didn't.

I've read quite a few investigation reports, and to me there is a clear difference in the level of detail between small accidents and major accidents. I doubt they retrieved the wreckage from the ocean for the JFK case simply because it is high profile.

@fluffysheap you are correct that the logs are not on the plane but you then must track the owner and have them turn the logs over assuming the FAA/NTSB did not take them as part of the investigation, in which case you would need to get them out of their hands which may not be a simple task.

@kevin The JFK Jr example was my intending to show that wreckage has been removed from hard to get to places even for small plane crashes. There is much debate as to why so much effort was put into that investigation but none the less it occurred. Some smaller crash reports are shorter/simpler because the cause is far more straight forward.

@Dave I don't think instruments are "airworthy" per se, but perhaps there's another term for what you mean. Salvaged equipment (of any kind) does need to be overhauled by an authorized source (e.g. the original manufacturer) before it can be used again.

I've read AAIB reports which go into a great deal of detail about complex GA crashes and others which are perfunctory. I'm sure "public interest" enters into it, but the main discriminating factors seem to be whether the cause is clear or obscure, and also whether anything is likely to be gained in terms of safety in the future.

The Cessna my father and brother were killed in crashed in in-accessible dense woods in Maine. The wreckage was never officially salvaged or removed.

Sorry for your loss. However, this doesn't address the question in full.

I think the implicit answer here is, sometimes it's just left in place. That is, in fact, responsive to the question IMHO.

One thing that often happens is that the wreckage is painted with a visible mark so that if it is spotted from the air again, it will not be suspected to be a new or unknown crash site.

Indeed. Gerry wrote that in a comment.

For commercial airliners, the airline logo is usually marked over. This sometimes shows up in the media portrayed as the airline's attempt at covering up, but in fact is done by the airline's insurer to mark that they have assumed ownership of the wreck and responsibility for the site.

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Is there a good iPhone app for tracking commercial aircraft?
I can see many airplanes circling around to land at KORD. I am wondering if there is a good real-time website or application to track these planes with 30-second accuracy or better. Any ideas?

I doubt it. Sounds likes a terrorist's wet dream, even if it could be used for plane spotters and the like

Hi Stu, welcome to the site!  This question has already been asked and has several answers which should answer your question.  My own answer on the question describes why the sites don't have real-time data available (it isn't allowed by the FAA unless you have an operational need).  If this doesn't answer your question, please [edit] it with the new info and we will consider reopening your question!

Great, thanks for the help. I will check out the other question!

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Have any airliners successfully landed on a runway after striking a tree?
There are many examples of aircraft striking trees during a crash sequence, usually with high fatality rates.
Have any airliners struck* one or more trees and proceeded to successfully land on a runway at an airport without any fatalities?
*Struck in this case meaning physical contact during flight which caused significant damage beyond scratches, such as denting, broken lights, partial loss of lift and/or control.
If I understand the terminology correctly, these incidents would be "Controlled Flight into Terrain (CFIT)" with subsequent airport landing without loss of life.
The closest I'm aware of is Scandinavian Airlines Flight 751 which lost thrust from both its engines and glided mostly into a clearing, striking trees as it went down.
Disclaimer: Long-time lurker, not a pilot, just enjoy the community and learning about aviation safety.

This is anecdotal and doesn’t involve an airliner, but I once flew into a small airfield in central Texas (which shall remain nameless). When I asked for fuel in the FBO, the owner said, “No problem.” Then he turned and yelled out the door, “Hey, Needles! We need fuel on the Piper!” Then he asked me if I knew why they called him needles... As it turns out, the guy flies a WWII B-25 in air shows. Once, upon returning to the airport, he got sloppy on approach and dragged the landing gear of his warbird through several pine trees on his way in. He was picking pine needles out for over an hour...

@AaronHolmes That B-25 wouldn't be named Devil Dog, would it?

Would you count planes which hit trees after landing, but failing to come to a stop before running out of runway?  (This sort of thing is probably far more common for small planes at small airports than with commercial airliners - they generally try not to have trees at the end of runways at the larger ones.  Though a flight at Midway, Chicago a number of years ago failed to stop due to ice on the tarmac and crushed a passenger vehicle on the street past the end of the runway.  I still maintain that Midway is a stupid place for an airport.

Not an airliner, but there was a case in 2005 in which a Cessna P210N struck a tree on take-off. The pilot believed it was a birdstrike, and that the aircraft was undamaged, and continued towards Portugal. He diverted to Jersey upon the port wing fuel tank reading empty. Upon landing it was discovered that section of the port wing was missing: http://www.aaiu.ie/node/208

These results might be skewed somewhat by the lack of trees near most airports.  If you're off-track enough to be near trees, your landing/takeoff is already well off the line.

A firefighting DC10 impacted trees during a drop.  Landed and needed some repairs.

Not counting overruns, specifically looking for in-flight incidents significant enough to pose significant survival risk that were overcome by pilots. Acknowledge this implies a significant deviation from an approved approach or flight route. Hadn't considered firefighting aircraft, which I presume would be at much higher risk of occurrence, thanks!

Yes, for example an MD-83 operating as American Airlines flight 1572 impacted trees on a ridgeline (and an ILS antenna!) on approach to Bradley Internal Airport in Connecticut in 1995.
It ultimately landed short with no fatalities and one "minor" injury.
The NTSB report AAR96-05 is currently here, but probably subject to link rot (so I'll post the actual text of a the link as an aid to re-finding it):
http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR96-05.pdf
As with many accidents, "there was a lot going on at the time" and it's not clear from a cursory reading what meaningfully contributed (vs what was present but did not ultimately matter) to the fact that the aircraft was lower than the crew though it was, or thought it should be.
That incident made the local news at the time; it's probable that there have been many others around the world.

Note: Since you are afraid it might disappear, it seems like the Wayback Machine has copies as early as 2010 of that page

This is pretty close to ideal example as requested, thanks! Interesting read, there was certainly significant tree damage before striking the antenna - which couldn't have helped - but was clearly at the tail-end of the flight.

And that's why ILS antennae are frangible, folks!

Report also available here.

Searching through the Aviation Herald database for incidences with the word tree, I found 3 cases:

An Eagle Air Let L410 contacted a tree during departure from Lankien in South Sudan. The right wing tip was damaged, but the aircraft continued to its destination, where the wing tip was repaired:

A China Eastern Airbus A320 contacted trees during a go-around at Wenzhou after losing visual contact with the airport during approach. The damages were only found after landing though:

A post flight inspection found scratch marks on the right main landing gear, slats and flaps of right main wing and the inlet of the right hand engine (CFM-56). An inspection of the right hand engine revaled damage (dents sized up to 0.2 mm) to all 36 fan blades, scratch marks (13cm in length) at and twigs embedded in the oil discharge.
[...]
Due to the late decision by the crew the right hand wing, right hand engine and right hand main gear impacted and clipped treetops outside the airport perimeter.

A Cebu Pacific Airbus A320 came in contact with trees, but the damage was also only found after landing:

a subsequent pilot inspection found branches and leaves embedded in the right hand main gear, the right main gear was leaking hydraulic fluid. The occurrence was rated a serious incident and is being investigated by Philippines's AIB.

Great finds! I wasn't aware of Aviation Herald. Your answer is very thorough and I appreciate the diligence. The Eagle Air flight meets the criteria, though all are fascinating stories. Thank you for your contribution, this is amazing! It's a tough choice, but I'm accepting American Airlines Flight 1572 primarily for being more dramatic.


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What does 'in-trim speed' mean with respect to Boeing 737 mis-trimming correction?
This question was prompted by discussions of the recent Boeing 737 MAX crashes, but it is not specifically about that variant.
In Boeing's 737 NG Flight Crew Training Manual, in Chapter 8 (Non-Normal Operations), under the heading 'Manual Stabilizer Trim' on page 8.16, it states:

Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.

In this context, does 'in-trim speed' mean the speed it is mis-trimmed to, the speed it would be trimmed to when put back in trim, or something else? For example, if the airplane is mis-trimmed nose down, and therefore, presumably, for a higher speed than intended, what action would relieve the airloads on the stabilizer, and why?
Additional information about what 'extreme cases' might require the airloads to be relieved in this manner would also be appreciated.

"In-trim" speed means whatever speed the airplane will naturally seek if you let go of the controls.  If you set the stab to position X, the airplane will naturally seek speed Y, for a given weight, thrust, flaps, and C of G condition.
So say the stab is at position X and this makes the airplane want to pitch to 240kt.  It will seek and maintain that speed if you don't touch the controls.  If you want to fly slower, you can add up elevator by pulling the column back, increasing the tail's downforce and pitching the nose up, until it slows to a speed where the forces are back in balance with the elevator held fixed at that position.  Say it's 200kt.
You are now 40 kt below trim speed, and having to hold the elevator displaced to keep it there.  If you want to be able to let it fly hands off at 200kt, you have to move the stab itself so that the tail's downforce with the elevator at neutral is the same as when the elevator was being displaced.  So you trim out the elevator displacement (by applying trim and easing the column back to neutral in little trial and error inputs) and now you're in trim at 200kt, hands off.
The 737 has a stab screw jack with a manual operation feature with a cable circuit between the screw jack and the trim wheels in the cockpit that let the crew turn the jack directly with the trim wheel, with no electric input, when in manual trim mode.
If you are way out of trim, that is, holding a lot of elevator to make the airplane fly slower or faster than its trim speed, it puts a large rotational moment within the horizontal tail which increases the up or down load on the screw jack itself.  These jacks are usually acme screws with dual load path threads that have a fair bit of internal friction under load, and the effort to drive the screw when it's highly loaded can be more than you can apply with your hand on the little wheel on the sides of the center console.
So say you're in manual trim and the airplane is trimmed to 280 kt and you want to slow to 200kt, and pull the nose up with elevator to slow down and you don't retrim as you're slowing down.  At some point, if the out of trim condition and resulting the load on the screwjack is high enough, you can't move the trim wheel because you can't apply enough force to turn the jackscrew.  To avoid this, you should be retrimming the stab as you slow down.
Their procedure is to try to offload some of the out of trim load on the stab jack by moving the elevators back toward the original trim speed.  If you were holding the column way back to slow to 200kt while the airplane was still trimmed for 280kt, you'd release some of the pull, letting the airplane pitch over a bit and accelerate, while trying to move the trim wheel.  At some point you'll have unloaded the stab screw jack enough to make the wheel move.  You don't want to pitch over any more than you have to so you just relieve the elevator enough to get the wheel to move, and keep working it along until it works normally.
In this context, "extreme cases" refers to the case of a large difference between existing speed created by elevator input and existing trim speed.

This seems reasonable, but it leaves me wondering why Boeing would not simply have written something like "reduce the force being applied to the control yoke"? Is there anything other than control forces to show you in which direction the current trim speed lies?

If you are holding column aft to maintain a speed, trim speed is higher and vice versa. Jets are quite different from trimming airplanes with fixed stabs with trim tabs on the elevator, where you trim until the column stays at the position you're holding it at.  With a trimable stab on a jet, you trim until you can release the column back to neutral. The column neutral location is always the same. With an electric trim, when slowing down you pull and blip and let it go, pull blip and let it go in a series of steps until the nose stays where you want it when you let the column go to neutral.

And it leaves me wondering why Boeing couldn't have inserted some gearing into the manual trim mechanism to provide the pilots with a greater mechanical advantage when retrimming a badly-out-of-trim aircraft.

In layman's terms it's saying the control forces might be heavier than normal when using only manual stabilizer trim.
The manual stab trim section of the Boeing book is explaining that if manual stabilizer trim is necessary (likely due to the electric stab trim having a failure), and the air loads are great, instead of ham-fisting the aircraft controls, it might be better to accelerate or decelerate to the trimmed speed, and then move the manual trim wheels.
Here's a hypothetical:
If a 737 for whatever reason is trimmed for 250 knots, but for whatever reason is flying at 200 knots, the aircraft will try to regain its trimmed speed.  This is absent any automation/autopilot.  This is basic aerodynamics inherent to any stable design from a Cessna 172 to a Boeing 777.  It is all due to positive static and positive dynamic stability. If the thrust does not increase, the only way to increase speed is to begin a dive and the aircraft will nose down & accelerate toward 250. (If allowed to accelerate, the aircraft would get real close to 250 and hold that speed closely, perhaps after a few oscillations).
If the pilots do not desire a descent, they might first react by pulling back to raise the nose and thus the speed will be lower than the in trim speed (which is also what the Boeing book is calling "mis-trim" speed).
Due to the aerodynamic loads on the stab, it may be very difficult to get the stab to move toward nose-up with the manual trim wheel.
Avoiding this difficulty is why Boeing's guidance is to get closer to the in-trim speed (even though it is NOT the desired speed and may even result in a unwanted climb or descent) before attempting to trim manually.
The final paragraph on that page:

"Anticipate the trim changes required for the approach. Configure the airplane
  early in the approach. When reaching the landing configuration, maintain as
  constant a trim setting as possible. If a go-around is required, anticipate the trim
  changes as airspeed increases."

Boeing is saying in layman's terms, stay ahead of the airplane with speed/configuration changes, don't waterski 2 miles behind the airplane (or bad things might happen).


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Will high blood pressure affect my pilot medical certification?
I will most definitely start a training for a glider pilot license at our local flight club. This of course requires a medical certification for pilots. The only concern I have, is my blood pressure.
I am an 18 year old male with an overall healthy condition. However the last few times I had a doctor's appointment, I had a somewhat high blood pressure (it was always between 150/70 - 180/85 mmHg). Online I haven't really found that much information about the limit of the blood pressure in order to still get the Medical.
I have found some sources saying that everything below 220/125 is good, but I think those sources we're only speaking about passengers of airplanes, not pilots.
For your info: I live in Germany, and I suppose there are other regulations regarding the medical in other countries, but overall I think the requirements don't differ that much.
Hopefully someone can tell me if I should be concerned or if my blood pressure is still okay to fly.

As far as I know, the normal blood pressure is 120/80 for a human. Your's higher value is a bit higher. It could be that you were in stress. Try to avoid salt and foods with excessive salt (french fries, chips etc).

I might add to the previous comment that the doctor's appointment itself maybe stressful. It could be the 'white coat' effect or related to the reason you went to see a doctor in the first place. You may ask for a 24-hour measurement (when feeling good). Not sure if this would help to pass any pilot test though (they might wear white coats too). This is not medical advice.

The white coat effect could actually be a reason for that my blood pressure has been high when seeing a doctor, but only slightly higher (if at all) than normal, when measuring it with my private blood pressure meter.

In the UK we don't need a medical to fly gliders, nor does the Doctor have to see you, they can sign a bit of paper, you sign it as well, and jobs a good 'un

I'm not a doctor but my girlfriend is training to become one. I have learned that blood pressure can fluctuate quite a bit from reading to reading. If you are stressed about the blood pressure test, it will almost certainly read higher than it regularly is. Try taking an average of ten tests over a span of two weeks or so.

Without knowing German, it's a little difficult for me to research the LBV's website, but I found this application for Validation of a foreign airman’s licence, and one of the requirements in it is:

Valid JAR-FCL Medical Class I or Class II

The JAR requirements for a Class I and Class II medical, both are:

JAR–FCL 3.135 Cardiovascular system – Blood pressure
(a) The blood pressure shall be recorded with  the technique given in
  paragraph 3 Appendix 1 to  Subpart B [at each examination].
(b) When the blood pressure at examination  consistently exceeds 160
  mmHg systolic and/or  95 mmHg diastolic, with or without treatment,
  the  applicant shall be assessed as unfit.
(c) Treatment for the control of blood  pressure shall be compatible
  with the safe exercise  of the privileges of the applicable licence(s)
  and be  compliant with paragraph 4 Appendix 1 to Subpart
B. The initiation of [ ][medication] shall require a  period of
  temporary suspension of the medical  certificate to establish the
  absence of significant  side effects.
(d) Applicants with symptomatic hypotension  shall be assessed as
  unfit.

It looks like you will probably need to lower your blood pressure (either via diet and exercise or with medication) in order to pass your medical.  If you start taking blood pressure medication, you will need to take it for a certain period of time to make sure that there are no other side effects before they will give you a medical.  You can discuss this with a medical examiner to see how the process works there.

Thank you. I forgot to mention that I also own a private blood pressure meter since a few weeks. My blood pressure never exeeded 160/95 since I started measuring. However I will consider diet and exercise to keep it as low as possible. There's still a few weeks until I visit the doc.

@Padarom Relaxation based biofeedback exercises may help more than diet and exercise.  I have personally lowered my systolic pressure (higher number) by 20+ points on a biofeedback system, and can make a significant change on demand.

@Padarom Go see a doctor. Not a flight doctor, but a "real" one. Especially at your age, 160/95 is elevated, and can cause you real harm over time. High blood pressure is serious stuff, because the damage happens unnoticed, and basically can't be fixed. The good news is, it can be controlled (the BP, not the damage), but you need to start sooner rather than later. Biofeedback/diet/exercise can be good solutions in some cases, and medication can also help. But get your BP down! Don't settle for "only" 160/95 or "it's just white coat syndrome." You'll be glad you did, 20 years from now.


text:
"Mixture, Pitch then Power" - why?
The above saying is taught as the process for initiating a climb when flying an aircraft with a constant-speed propeller (and the opposite order for a descent). Why is it the case?
I was originally taught a vague explanation saying that low RPM and high manifold pressure could lead to detonation, but how?
I believe the need to enrichen the mixture prior to a climb is purely for engine cooling purposes, not anything to do with the stoichiometric ratio, please correct me if this is wrong.

This is mostly about when going balls to the wall, but is generally applied to more gentle power applications as well to make it an automatic SOP, and just to go easy on the equipment. Also it's not end of the world on a non-boosted engine to violate it, but it might be on a boosted one.
At max power, you need a full rich mixture both for cooling and detonation margin purposes. It's also good to go to high RPM before manifold pressure because detonation margins are in part a function of Brake Mean Effective Pressure in the cylinder and raising manifold pressure suddenly without speeding up the air pump (engine) tends to spike BMEP.
On a normally aspirated engine, violating these rules won't blow it up (not on an engine running 100 octane and a compression ratio of 8:1 - in car world that would be easy street), but on a turbocharged or supercharged engine the risk is significant and it's good to be consistent with technique as well as just going easy on the machinery.
A secondary factor is if you go to wide open throttle and follow with max RPM too quickly, the governor won't be able to keep up if the change was large and the torque level is maxed out, and the prop will overspeed momentarily as the governor overshoots (everybody on the ground will know about your sin by the YEOOOOOWWWRRR sound).
Anyway, if you're going to climb at maximum power at lower altitude, you do need to go full rich, mostly for cooling but if you are just going from some econ cruise setting like 20" and 2100 RPM to, say 24/square to climb, I might just enrich a little to maintain the EGT and not go full rich.


text:
Is Ground Direction Finding commonly used?
I've recently come across the concept of Ground Direction Finding. My (limited) understanding of it is that it is a system that allows you to see where a VHF transmission is coming from. I gather it was used in the Earhart-era of aviation for navigating, and could be a rudimentary air-traffic control system where there is no radar.
I think it's still used these days in boats but what about aviation? And is my understanding of it essentially correct?

Do you mean VHF Direction Finding (VDF)?

https://en.wikipedia.org/wiki/VHF_omnidirectional_range

@xxavier That's not it. VDF is something else entirely from VOR.

@J.Hougaard  Yes, you are right. The OP asked about a ground based system...

@J.Hougaard The book I am reading mainly refers to 'ground' but VDF seems to be the correct term...

Yes, it is commonly used, especially in large complex airspaces.
If two VHF direction finders are installed at sufficient distance from each other, they allow the ATC system to triangulate the position of a VHF transmission. This position is then indicated on the air taffic situation display, which helps the air traffic controller to quickly correlate the transmission to the transmitting aircraft, often before the callsign has been transmitted. The controller still has to crosscheck the callsigns, but it helps to reduces workload.
Example of a VHF direction finder


text:
What is the difference between Full Throttle Height and Critical Altitude?
My understanding is that "critical altitude" is the density altitude at which the wastegate on a turbocharged engine is fully closed, so any climb will result in a decrease in manifold pressure.
Is this different to "full throttle height"? I have heard conflicting definitions of that, such as it only applies to superchargers, or that turbocharges have multiple full throttle heights.

Many people consider Full Throttle Height and Critical Altitude to be the same thing. I think any answer depends a lot on the actual engine type, and is complicated by turbocharging vs supercharging, and further complicated by engines that have both a supercharger and turbocharger, or 2 speed super chargers. Intercoolers and water injection also muddy the water.

Bob Tait explains it perfectly:

Every turbo charged engine has a rated boost which is the maximum manifold pressure permitted for that engine. It is marked as a red line on the manifold pressure gauge. Because the ambient density drops with altitude, there will always be an altitude beyond which it will be impossible to obtain the rated boost. That is called critical altitude.
However the aircraft is still capable of climbing beyond that altitude but the manifold pressure available at full throttle will be less than rated boost. For every value of manifold pressure there will be some other altitude beyond which that particular manifold pressure will no longer be available. So every value of manifold pressure has its own full throttle height. Critical altitude is simply full throttle height for rated boost i.e. the red line on the manifold pressure gauge. (bobtait.com.au)


text:
What degree of elevator deflection is required to takeoff?
I've always wondered how much the elevator actually needs to deflect in order to cause rotation on takeoff for a large airliner. On videos I can rarely see the elevator moving at all.
I'd really like to know what the degree required is for a 777, but if someone can provide this for another airliner that would be ok. I presume that it depends on takeoff speed, which is of course variable, but let's see what you can come up with.

Degree measured from what? The elevatot doesn't have to deflect much because the whole stabilizer is already turned to an optimal setting for take-off. Even the angle of attack for the stabilizer would be hard to say since it depends on speed, weight and center of gravity.

@Sami The stabilator AoA might not be hard to see. On the EMB-145, e.g., it is almost always +8 degrees for takeoff and if you look closely (on ours at least) there is a scale painted on the tail to visually read the stabilator AoA.

There's a scale on the tail of E190 also. I'm pretty sure it's not degrees though. Even if it was, I would still find it difficult to determine the elevator angle during takeoff.

Stabilator settings vary by CG, takeoff weight, and power setting. In Boeing 747 manuals they're in section 1-06-001. You can look at an example at http://terryliittschwager.com/WB/manuals/Boeing_747-400BCF_GPR1_WBM.pdf starting at the 71st page of the pdf. I don't know how to convert from the stab units to degrees.

@casey Sorry, I was wrong. They are degrees. Just checked..

It depends. Mostly on two parameters:

What is the position of the center of gravity? A more forward position would require a bigger downforce at the tail, so deflection angles would be bigger. On the 777-200, c.g. positions from 14% to 44% of MAC are allowed.
What is the trim setting of the stabilizer? Depending on the setting, more or less deflection is needed to set the whole horizontal tail to the right downforce for rotation.

Further parameters are flap settings, take-off mass, rotation speed and desired rate of rotation, but the first two are the most important.
Since I do not have the official Pilot's Operating Handbook for the Boeing 777, the virtual version has to do. Sadly, it contains very little information. The more seedy corners of the internet have maybe more substantial content, but here you are on your own.
The Boeing 777 has a computer based weight and balance system, called Accuload, which will compute the proper take-off trim setting, therefore, no discrete values can be given. With the recommended trim setting, the pilot will apply forward pressure on the control column until roatation speed ($v_R$), relaxing control forces to neutral for smooth rotation.
If you would take off with the trim setting for cruise, the elevator would need to be deflected by approx. -10° (trailing edge up) in a simulation with typical parameters. Please note that this is not the regular take-off procedure, and the actual deflection angles are much smaller.

Helpful? Elevator Design.


text:
What makes someone a 'Senior First Officer'?
Some airlines have a Senior First Officer rank. Apart from the title and (presumably) the pay, what makes them different from a regular First Officer?
Do they have any differing duties or responsibilities? And do they need to pass some kind of test, or is the rank just given to them after a certain amount of years service?

From Wikipedia: "Often the senior first officer position is used within airlines to mean someone who has passed all the requirements for captain, but there are no empty captain's positions within the company as yet" (a captain may become a senior FO, if there is a decline in the business -- source). A senior FO may opt to remain FO to continue without the additional responsibilities of a captain, and may become a senior FO with more flying experience than a junior captain.

@mins an additional issue is that a first officer with a lot of seniority with have a lot of choice about routes and schedule.  When that pilot becomes a captain he, or she, will typically be very low seniority, so will have little choice about routes and schedule.  Typically, the crews that end of flying on Thanksgiving day, etc are a junior captain, junior FO, and junior flight attendants.

@Adam -- you do have to take "green on green" rules into account

@UnrecognizedFallingObject - can you give more detail (or a link) on "green on green" rules?

@FreeMan -- "green on green" rules forbid the pairing of a low-time captain with a low-time F/O to make sure there's somebody in the cockpit who isn't fresh out of training.  In some companies, this is based on "time in company" instead of total-time, even -- this may apply where specialized flying is taking place.

Thanks, @UnrecognizedFallingObject, that's what I thought, but I figured clarification would be good.

Not an opinion, but an actual rank. Voting to keep open.

Have heard of a pilot who failed the captains' exam twice and became a senior first officer. He has an extensive flying experience, longer on type than most, and is teamed up with freshly graduated captains. Last I heard, pay was good.
It is some years ago, before covid and at the time of severe pilot shortage worldwide, and at the time after two attempts there were no more opportunities to graduate to captain. The choice was to remain senior first officer at the airline or leave for another and go for captain there.
This is a single case that I've heard of and I do not want to make the suggestion that this is always the case. It is essential for airlines to be able to couple experienced captains with novice first officers and vice versa, senior first officers simply have an essential role to play.


text:
Does angle of attack change in a sustained climb?
I saw this question on a closed Facebook group, generating wildly differing answers. So I thought I would ask it here.
You're in a C172 flying straight and level at 5000 feet and 100 knots IAS. You apply full power and go into a sustained climb maintaining this airspeed.
Has the angle of attack increased, decreased, or remained the same?

This question needs a more specific scope or you'll be trolled by people who will be like, "well by the time you climb into space you will probably start to stall from the increase in angle of attack needed to compensate for the reduced air density."  What I think you want to know is: not really.  At first it increases due to initial acceleration upward, then  the angle of attack will probably decrease to a lower angle than at level flight due to the vertical thrust vector making some of the work from the wings be done by the engine's thrust vector... until the air gradually gets too thin.

This is a trick question. At 5000 and 100 KIAS a C172 is already at full power. Well, almost ;)

We have seen that

A climbing aircraft needs less aerodynamic lift than in horizontal flight, not more.

this means that if we keep constant airspeed and if we do not alter the configuration, the angle of attack will be (slightly) smaller, at least until the air density does not change.
As your assumption is that

You apply full power

to enter the sustained climb, you will have even more thrust during the climb, and this will reduce even more the needed lift. This, together with the fact that you are slightly accelerating, reduces even more the angle of attack.


text:
How much hydraulic fluid is in a jet airliner?
Hopefully the title is self-explanatory. I am wondering how much hydraulic fluid - in mass and volume - is carried in normal operations for a jet (the bigger the aircraft in your answer the better).

FCOM for the A320 describes 3 independent hydraulic systems, with accumulation reservoirs for each at 6.5L,12.5L & 14.5L (1.7USG,3.3USG& 3.8USG) respectively, so +33.5 liters is a good bet, which translate to 26-33 kgs depending on fluid type.
Note that more fluid will be available in the system, but how much exactly you will need a mechanic to answer.

The reservoirs are only a small fraction of the hydraulic fluid in the system. Most of it is in the hydraulics tubes and actuators.


text:
Do large airliners have a short-field landing technique?
Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners?
In discussions about the famous landings at St Maarten, it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway.
Such a procedure is fine in a Cessna, but in a large passenger jet? I have my doubts.

Other than the weight restrictions - there are no short field requirements for large jetliners.

Do airliners allowed to operate from London city airport count? The steep approaches may be a specific landing technique.

@ManuH, steep approach are certainly a specific landing technique, but the reason for those is either noise abatement (in case of London City) or obstacle clearance (in case of some airports in mountainous regions), not short field.

Come down slowly and really low hit a hill before the runway and loose a gear or two and scrape your engines to stop in 1/4 of a 5000 foot runway with a 747. ~ True Story

Worth noting that getting an early touchdown is more about maximising margin for error and comfort than anything. While the runway is "long enough" for a 747, it's nice to have an extra couple of seconds of reaction time once you realise your thrust reversers have failed to deploy, and it's more comfortable for the passengers not to have to stand on the brakes in a regular landing

Related

You can always put a plane down in a small area. Note that containing the fragments and blast effects can prove challenging...

@JonStory: ...and also an extra couple of seconds for the airbrakes and wheelbrakes to slow you down.

In Jets you always aim for the touch down markers which are 1,000 feet down the runway. The short field technique is to not miss those.

Is this question intended to include emergencies and intentional high-performance flying, or only routine operation?

@Tom W it was intended to ask about approved procedures in routine passenger-carrying airliners, to debunk the excuses at SXM. If there is an approved emergency procedure I would be interested (not the type where "all bets are off, do whatever you need to do to survive")

Other than extra braking and reverse thrust, is there a specific short-field landing technique for large jet airliners?

Never heard of any. The required landing distance is calculated so that the plane can reliably stop (even if reversers fail) and landing at shorter runway is not allowed.

so the 747s try to land right on the numbers, rather than the usual technique of touching down within the first third of the runway.

The usual technique is to aim for 1,000 ft down the runway and touch down with some flare somewhere around 1,500.

In discussions about the famous landings at St Maarten, it is sometimes said that part of the reason for the low passes is due to the relatively short runway, so the 747s try to land right on the numbers

Actually the TNCM runway 10 has PAPI and TDZ marking a little beyond the usual 1,000 ft mark at around 1,250 ft. Ourairports says the threshold is displaced 162 ft (but it also says runway 9, so it is likely out of date), but according to the satellite images it is a bit over 300 ft plus some runway end safety area, placing the threshold around 500 ft past the fence and the touch-down zone around 1,750 ft past the fence.
Now the normal glide-slope is around 5%. That means the aircraft is supposed to cross the fence at around 90 ft, on average. That seems about right. Of course you can't expect every aircraft to be positioned precisely within a few feet, so now and then some crosses it at maybe 50 ft. That is not intention, but simply a deviation. But of course the photos of planes flying especially low are more likely to be picked for publishing.
Also, a short field landing normally calls for steep approach which make precise aim for landing spot easier. That would actually place the aircraft higher over the beach. But the glide-slope at TNCM is normal 3° (5%) one, so it is not a steep approach.

Such a procedure is fine in a Cessna, but in a large passenger jet? I have my doubts.

In large jet it isn't. Air transport has stricter regulations than general aviation because more is at stake and larger aircraft have stricter limits because the higher energies involved mean errors are harder to fix and have more serious consequences.

I'm not aware of any short field landing techniques for large commercial airliners. But some of the do offer some modifications, that offer improved short field performance. Most of these modifications are aimed at operating the airliners at the Santos Dumont airport, which has a short runway. According to Boeing,

The short-field design package is an option on the 737-600, -700 and -800 and is standard equipment for the new 737-900ER. The enhancements increase payload capability for landing up to 8,000 pounds on the 737-800 and 737-900ER and up to 4,000 pounds on the 737-600 and 737-700.

This is mainly done using a few modifications, which can be factory ordered or retrofitted and include the following changes:

Flight spoilers are capable of 60 degree deflection on touchdown by addition of increased stroke actuators.
Slats are sealed for take-off to flap position 15 (compared to the current 10) to allow the wing to generate more lift at lower rotation angles.
Autoslat function available from flap 1 to 25.
Flap load relief function active from flap 10 or greater.
Two-position tailskid that extends an extra 127mm (5ins) for landing protection. This allows greater angles of attack to be safely flown thereby reducing Vref and hence landing distance.

among others. Around 250 of these modified aircraft are in operations till date. Not to be outdone, Airbus offers similar options in its A320neo.

Note: I'm not sure if this is what you've asked (which @Jan Hudec has answered already), but I've added it just for info.

The short field technique in any jet is to perfectly hit the touchdown zone marker which is 1,000 feet down the runway. They’re 150ft long. Landing on the numbers in a transport category jet would fail any checkride.

I would argue there is nothing in the books specifically called ‘short landing technique’ as any landing in a jet is already designed to be as short as possible. Then it becomes a ‘normal landing technique’.
Sure, if you have many 1000’s meters to spare, you might occasionally go for a greaser and land longer than usual. Generally speaking though, the shorter your flare, the safer it is; more runway left to slow down, maybe reducing the need for reversers or easing up on the brakes so as not to heat them as much.
In that sense, a normal-SOP-landing on a transport jet is already a short-landing-technique.

authors: Bob Jarvis - Слава Україні


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How do airliners prevent raising the gear on the ground?
GA aircraft use a squat switch to prevent accidental retraction on the ground. Do airliners use a similar system? I've heard some reference to a manual pin, I'd appreciate clarification on that.

related: http://aviation.stackexchange.com/questions/8303/have-landing-gear-collapsed-at-the-gate

Most airliners have a protection system for this which is based on Weight-on-Wheels (WoW): sensors which detect load on the wheels (which implies that the aircraft is in contact with ground). For safety reasons this can be bypassed and there's usually a small lever in connection to the gear lever to do this. This image illustrates the 737 gear lever where you can clearly see a "lock override" which fills this functionality (red part)

It is important to note that if you pull the override switch on the ground, you can move the handle, and the gear WILL come up.  The WoW sensor only prevents lever movement, not gear retraction.  Some planes may be different if course.


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How exactly am I supposed to notify ATC when I fly my drone? (UAS)
I recently registered my new 250 class Quadcopter with the FAA under the Part 107 sUAS code. I want to fly within the regulations, and the only one that I'm really unsure about how to abide by is the "notify ATC" restriction.
I live within 5 miles of a couple small airports in the California South Bay, which apparently makes me need to legally notify nearby ATC whenever I fly. How can I do this?
I saw this other post which talked about how to find the telephone numbers for ATC in your area, but are these the people I need to call? And if so, with what information would I need to give them? I also saw this other post that discusses how to call ATC, but is the information there current and relevant to my flights?
Thanks,
Neil

At first glance this looks like a possible dupe of the second question you mentioned. What exactly is not answered in it? Or are you just concerned that the information may be outdated?

I'm mostly concerned with the latter, @Pondlife. I saw this FAA article that says that I need to give the FAA 90 days notice to my flight, and this other article that says I can do it from an app. Both sources appear to conflict one another, and I just want to be sure that I am doing the right thing.

I really don't want to have to wait for 90 days for permission to fly, especially since my decisions to fly may very well be spur of the moment decisions.

@ifconfig The first link in your comment is regarding Part 107 waivers. Since you're talking about notifying ATC when you fly, I'm assuming you're flying as a hobbyist instead, and so getting a Part 107 waiver doesn't apply.

@ifconfig That said, I am sympathetic to your question. There are currently two answers on the second question you mentioned, neither is marked as the answer, and only AJ Henderson's is complete and correct. I'll write an answer later today if no one else does first.

This question may well be obsolete due to recent changes in regulations, and the introduction of the LAANC authorization system.

If you are flying as a hobbyist
If you are flying as a hobbyist, which seems to be the case, you are required by Public Law 112-95 FAA Modernization and Reform Act of 2012 section 336 to:

(5) when flown within 5 miles of an airport, the operator of the aircraft provides the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport) with prior notice of the operation (model aircraft operators flying from a permanent location within 5 miles of an airport should establish a mutually-agreed upon operating procedure with the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport)).

This, of course, does not say how you are to contact the airport operator and air traffic control. The traditional way would be to find the telephone numbers for the airport and air traffic control, and to call them. Alternatively, as you discovered, some mobile phone apps allow you to electronically submit notices to some airports. What is not required or desired is to contact ATC by radio. If you are operating very near an airport, it may be a good idea to get a radio so that you can listen in.
If you are flying under Part 107
If you are flying under Part 107, you do not have to contact the airport or air traffic control even if you are within 5 miles of an airport, but you must not fly in controlled airspace without obtaining an airspace authorization or airspace waiver. These processes are, at this time, handled through the FAA Drone Zone website, and not by contacting the airport or ATC. Depending on the terms of the authorization or waiver, if granted, you may be required to contact ATC prior to operation, and they will need a way to get in touch with you.
Which rules do you need to follow?
Broadly, if you're flying for fun (e.g. as part of an enthusiast group, in your back yard, or taking personal photos in the park (although watch out for people as per the safety guidelines you are following)), you are a hobbyist, and subject to the special rule for model aircraft.
If you're flying for commercial or business purposes (e.g. taking photos of houses for real estate sales, inspecting railroad tracks, or delivering purchased packages), you need a Part 107 license and to fly under Part 107 rules.
For more information, see the FAA's sUAS FAQs and the table on page 11 of the FAA's interpretation of the Special Rule for Model Aircraft (pdf).

Thank you for the clear explanation, @Dranon. The waiver situation makes more sense now.

My only question is what is the difference between flying as a hobbyist and needing a Part 107 license. When is one required or better to use over the other?

@ifconfig I added a small section to address this. It's only a broad overview, but it should serve for general purposes.

Thank you very much, @Dranon. The explanation was more than sufficient.'


text:
Do unused parachutes need to be repacked? If so how often and why?
I was reading some military fiction and saw a comment that army airborne operations were required to repack all parachutes every ninety days, allowing parachutes that were due to be repacked soon to be cheaply used for training. This got me thinking: do parachutes need to be repacked on a schedule? Is this uniform across all types of parachutes and use cases? (are there differences between military and civilian requirements?) How long is the repack cycle? Why is scheduled repacking needed?

Ususally, the mandatory packing intervals are mentioned in the chute description, see e.g. http://www.strongparachutes.com/library/Documentation/Emergency/Para-Cushion%20303%20Manual.pdf (in this case 365 days for an emergency chute).

Yes, parachutes need to be repacked regularly. The length of the interval depends on the material of the parachute and is between 60 and 180 days. Every parachute should have a small pocket with a piece of paper which lists the most recent repack date and the name of the packer (who needs to comply with FAR part 65, subpart F).
FAA part 91.307 says:

(a) No pilot of a civil aircraft may allow a parachute that is
  available for emergency use to be carried in that aircraft unless it
  is an approved type and has been packed by a certificated and
  appropriately rated parachute rigger—
(1) Within the preceding 180 days, if its canopy, shrouds, and harness
  are composed exclusively of nylon, rayon, or other similar synthetic
  fiber or materials that are substantially resistant to damage from
  mold, mildew, or other fungi and other rotting agents propagated in a
  moist environment; or
(2) Within the preceding 60 days, if any part of the parachute is
  composed of silk, pongee, or other natural fiber or materials not
  specified in paragraph (a)(1) of this section.

The reason should be clear from the regulation: If moisture is present, the growth of mold may prevent the parachute from unfolding easily.
For the T-10D parachute, which is the standard US Army parachute for airborne assault operations, the repack period is 120 days.

Why does it need to be repacked? I assume there is a real reason for the regulation.

@hildred: Yes, I added the reason. If I find a difference between military and civilian requirements, I will add that, too.

@hildred during repacking the rigger would also check the parachute for damage and mold. If he finds any then he won't repack it.

Intervals go up to 365 days for emergency parachutes, too (may depend on country)...

Can mold be that bad that it hinders unfolding? It's a bit hard to conceive. Are there mold infested parachutes discovered during repacking typically?

@curious_cat: When they are stored well, no, mold is not found. Repacking includes also an inspection, and if mice have nibbled trough the risers, the packer should find this as well. If you could not observe the well-being of the parachute closely over the last months, repacking it is a small price to pay for your peace of mind. Parachutes also have a best-before date; note the Wikipedia page on the T10.

@PeterKämpf Mice! Yes, to me mice sound a far more credible threat than mold sounded. I'm totally with you about the peace of mind bit. Just that the mold threat didn't sound as credible. OTOH Mice do sound very bad and likely.

@PeterKämpf: Actually, I'd love to do an experiment of the sort where one takes a (synthetic e.g. Nylon) parachute, sprays it with a mold spore culture and then on purpose stores it in something like a damp cellar for a year to just see how bad things can get. Maybe then get an enterprising elite paratrooper to jump with it (and some sort of very reliable reserve of course). :)

@curious_cat: I did, with random cloth in a cardboard box. If it has some impregnation, the cloth will stick together over time. Now think that someone spilled beer over the canopy and then packed the chute after drying. Moisture will crawl in over time and make the cloth stick together. There are many ways this can work, and the longer the cloth sits in the same position, the worse the sticking gets. And in the end it's not a matter of opening at all, but opening before you hit the ground. Sometimes this makes all the difference.

@curious_cat If you wanted to do that experiment safely, you'd rig the chute to deploy automatically and attach it to a dummy (or other human sized test weight) for the drop.  Then all you need to do is make sure no one's in the splat zone if it fails.

@DanNeely There are special parachute harnesses (rigs) used for testing parachutes that hold three of them.  The one being tested, the "main" parachute, and the emergency / reserve parachute.  Then it doesn't really matter if the one being tested fails.

I'm adding this as an answer, because it is too long to be a comment, but it is meant as a supplement to the already accepted answer
As a skydiver of 13 years, and having been a member of two different national teams and three different national skydiving associations (US, NO, DK), I will add that repack cycles are in most countries/states defined for reserve canopies. Both main and reserve canopies have main control inspection intervals as well, where a repack also occurs, ofcourse. The intervals I've come across differs. Student gear have in most cases more frequent cycles, due to the fact that they land in trees and similar, more often than experienced skydivers. Reserve canopies seems to have cycles that somewhat depends on climate, more specifically humidity. Florida for instance has the most frequent reserve repack cycle I've come across. I think it was three months. In Norway however, it is 12 months. I am not a rigger (an educated skydive-gear god), and I haven't checked this specifically, but my impression is that the opening functionality of a canopy might be compromised if it stays compressed for too long, and that humidity speeds up this process. We like the opening sequence to be as predictable as possible, and even though it would probably work anyway, it is better to be on the safe side. It is generally recommended to keep your main canopy unpacked if you are not going to use it for a while, as long as it is not exposed things that might compromise fabric or lines.
Military gear is sometimes round canopies, instead of the standard square sports-canopy. I have no idea how the round ones needs to be packed, but from what I've seen of the military square-jumpers, I wouldn't be surprised if they have the same repack/control cycles as student canopies, and for the same reasons (trees).
I normally repack my main canopy before jumping, if it has been more than 3 months in my container.

When I started flying hang-gliders, there were a number of incidents (some fatal) where reserve chutes were thrown but did not deploy properly.  Competence at chute-packing was the main cause, but some came from chutes where the fabric was simply too stuck together.  Clubs started running chute repacking days in local halls or sports centres, sometimes with a zip-wire from the roof which would let you practise throwing your chute under realistic conditions.
For our reserves, we tended to reckon on repacking being a yearly activity, but then many people would go their whole flying career without ever throwing their reserve.  More frequent repacking was not justifiable given the odds of needing it.  If you're skydiving or doing military airdrops, using the chute is non-negotiable, and reducing risks by more regular repacking is very sensible.

Doesn't the reserve have to be packed by a certified rigger?

Differing civilian and local regulation, and probably not under the same FAA regulation as an aircraft.

@curious_cat Kind of.  In practise clubs would generally have someone who was competent to do it and would supervise.  Alternatively you could give it to a local school/shop to be repacked "officially".  Hang-gliding isn't highly regulated, and really it comes down to making your own choices about risk.  Chute repacking isn't difficult, you just need to get it right.

@Graham Thanks. The protocol I assumed was you can pack your main chute but a certified rigger must pack your reserve.

If you go into a glider hangar, you'll find a bunch of club chutes, all of which have been repacked before the beginning of the season, and last 180 days. Sometimes the chute has a pocket for the log, other times it's under one of the flaps.
I always wonder how much risk there would be  flying in a glider with a slightly outdated chute at the end of the season.


text:
Are afterburners required to be engaged during catapult launch?
Is it required to engage afterburners during catapult launches from an aircraft carrier?
This answer mentions that afterburners are used for night takeoffs as per regulations, but not required during day takeoffs. Is this true? If yes, why?

I think this is a big "it depends". Not all aircraft types have afterburners. For those that do, it might depend on things like takeoff weight or other factors.

The short answer is very much "no" -- afterburners are not at all required to launch from an aircraft carrier.  Longer answer: Fred Larson's comment is correct: it really depends.  Ultimately a given aircraft, at a given weight, with a given wind-over-the-deck, and a few other things, requires a given amount of thrust to get airborne -- whether it comes from dry thrust or afterburner doesn't change the requirement.
There are a large number of carrier-based aircraft (the A-7, A-6, and E-2 leap immediately to mind) and there are certainly others that flew off-deck without afterburners.
Current aircraft like the F/A-18 Hornet can be launched without afterburner in some, but not all, configurations.  For the most part the incremental safety margin and increased take-off weight means that afterburners are used for takeoff, but it's not strictly a requirement.

Also, the C-2 Greyhound Carrier Onboard Delivery aircraft is a turboprop - no afterburners there, either.

It depends on the aircraft type, loadout, fuel aboard, required endspeed, weather and winds, etc.  Some jet aircraft or carriers e.g. the S3 Viking, A-6/EA-6B, A-7 etc.  did not use engines equipped with re-heat, so that was not an option.   Earlier incarnations of the F-14 required the use of reheat during cat launches due to the low thrust and temperamental nature of the older TF-30 engines; when the GE F-110 powered F-14B and D variants arrived on ship they allowed for launch without the use of afterburning for most load outs and mission profiles as the newer F-110 engines had a max dry thrust on par with the TF-30’s downrated afterburning power output!  The F-404 and F-414 have been solid and reliable power plants for the F-18 series fighters and usually don’t require the use of reheat for light loadouts.   Again the flight crew will have to make that decision based on the factors described above.


text:
Is any air-to-air missile capable of re-engaging a target after missing?
Unfortunately this question is prompted by missile performance in a community mod for DCS, where an Israeli Python-5 is depicted as missing its target, completing a vertical loop, then re-engaging and hitting the target.  The idea is really unbelievable to me, but I haven't kept up with modern air-to-air missile technology.  Is anyone claiming to possess missiles with re-attack or re-engagement capability?
I haven't found anything by Googling for "can air to air missiles re-attack" or "can air to air missiles re-engage".  I've seen claims that the Python 5 can engage "any target at any angle, including backwards launch" and I could see how a Lock On After Launch capability could be evolved into a Re-Attack capability, but they're clearly distinct.

This doesn't seem to be about aviation, rather weapon technology.

@mins so are existing questions with upvotes and answers, like Can anti-radiation missiles be used to target stealth fighter aircraft?.  This is a question about military aviation.

Almost all homing weapon will try to engage something, and sometimes does engage something, after losing its original target.

@user3528438 do I need to clarify that I mean re-attacking the same target?  I mention the Python 5 looping around, but I could emphasize it more

@use3528438,  "Almost all homing weapon will try to engage something" This is not true. I cannot say with certainty that NO current AAM can do this, but the AIM-7 Sparrow, and the AIM-9 Sidewinder, and all Soviet AAMs when I was on active duty, absolutely cannot do this.

@Charles Bretana The aim-7 could re-engage on loss of RADAR lock on the F/A-18A. The hornet tilts the RADAR planner array forward and out of the way. A flood horn located behind is then used to blast the whole area with RF energy in the hope that the missile will get some sort of a reflection off the target. I suppose it comes down to the definition of missing. If breaking primary lock on a non-fire-and-forget missile would otherwise cause the missile to not receive steering commands, that's as good as missing in my book,

@Craig re-acquisition of target after losing lock, but while the target's still in front of you, isn't quite what I had in mind with this question, though it is interesting

@Craig,  In the F-4 (USAF) this was called Wide gate. We also had a flood antenna. The doppler speed gate in the missile would sweep the entire range of possible velocity doppler frequencies. But it would almost always lock on to the ground return (Main Beam Clutter).

Yes... there are two missiles air to air (Python 4/5) that could "re-engaging" its bandits!
The following diagram is reproduced from "Air Power Australia" by Dr. Carlo Kopp. ausairpower.net/TE-Gen-4-AAM-97.html

interesting!  what's the source for that diagram?

From the famous "Air Power Australia" by Dr. Carlo Kopp... http://www.ausairpower.net/TE-Gen-4-AAM-97.html


text:
What "jet engine" is featured in this ad that Simone Giertz made for a phone?
Simone Giertz's video "Having Dinner With a Jet Engine/Leaf Blower" has a number of views of the turbine, on a cart, with a ducted fan attached.  This side view is the best view, in my opinion.

I put "jet engine" in quotes in the title because it doesn't seem like it's trying to produce thrust via exhaust, it looks like a turboshaft or turbine generator or maybe APU where the power is supposed to go into the output shaft and the hot exhaust just comes out the side, slow.  I'm guessing the ducted fan is an add-on but am not sure.
There's also a good shot of the control panel during start-up.  I haven't immediately noticed one that shows operating RPM.

At least one shot also shows a nameplate top-front on the compressor section but it's not in focus and I can't make it out.
I feel the need to postfix this with:  I am not in any way affiliated with Simone Giertz or Google.

The screenshot clearly shows one gauge labeled "__T SEC RPM" (probably "hot section rpm"), and the one at the far left seems to also be something RPM, though it's too out of focus to be sure. Big gauge between them seems to be EGT - exhaust gas temperature.

Sorry, what I meant was I didn't find any parts of the video that show the RPM gages reading other-than-zero as a clue to the operating RPM range (which could help in classifying the thing?), which doesn't appear to be marked on the gage.  The gage on the far left is "Gas Producer RPM" (it's more evident in other frames near the same time code).  I believe the RPM gage near the starter controls is "OUTPUT SEC RPM", also more evident from the adjacent few seconds of video.

The engine seems quite obviously to be a Boeing T50 Turboshaft Engine variant, T50-BO-8A is a very, very close match, you can see pictures and info here:
National Air and Space Museum: Boeing T50-BO-8A
All major visible features are exactly the same, some minor parts are different, but may have been switched by current and/or previous owners.
Engine concept dates back to late 40's.
I did not add a picture here because of the copyright restriction posted on the National Air and Space Museum website.

Oh wow.  It's pretty striking how, with the clear nameplate shot on the NASM site showing where it is and the right size, I can now baaaaaaarely see the Boeing stamp on the nameplate in Simone's video.  I agree that this is most likely correct, or at least correct enough for my curiosity, so I'll wait the customary 24 hours and then accept.

@Erin Anne sometimes the brain needs a little help seeing stuff, since you basically can't see what you are not looking for :) I myself had no idea Boeing had ever made turbine engines...


text:
Is the rotor described in this Kickstarter new?
A NewAtlas story linked to a Kickstarter for a the "Whisper Drone" that shows a CAD model of a rotor that the Kickstartee-aspirant has apparently 3D-printed and flown (four of) on a quadcopter.  I find the rotor strongly reminiscent of something I can't place.
Is the rotor design new?  If not, what is it (presumably a variant of)?

I believe this is essentially a centrifugal duct fan that you'll find in some vacuum cleaners -   http://www.heko-electronic.com/home-ventilation/vacuum-cleaner/ec-centrifugal-duct-fan-for-vacuum-cleaner.html

The rotors on that drone are of the centrifugal fan type. They are not new in design (don't know about aircraft use though) and can be found in all kinds of everyday appliances: hairdryers, vacuum cleaners, car A/C blowers, etc. They move air at a 90° angle, sucking it in from the top and expelling it from the side.
Apparently they are more silent in this application than a normal propeller (or so the kickstarter claims) but it is easy to spot some downsides. Weight for one thing, as it seems they need a lot more material for construction than a normal prop.

Hmm.  It looks like the ramp that drops out toward the edge also provides an axial thrust component.  I agree it seems like a variant of a centrifugal fan though.